Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INJECTOR TIP ASSEMBLY AND METHOD OF FUEL INJECTION
BACKGROUND OF THE INVENTION
The subject matter disclosed herein relates to gasification and combustors.
More
particularly, the subject disclosure relates to injector nozzles for
gasification.
Many known integrated gasification combined-cycle (IGCC) plants include a
gasification
system that is integrated with at least one power-producing turbine system.
For example,
at least some known gasification systems convert a mixture of fuel, air or
oxygen, steam,
and/or CO2 into a synthetic gas, or "syngas". The sysngas is channeled to the
combustor
of a gas turbine engine, which powers an electrical generator that supplies
electrical
power to a power grid. Exhaust from at least some known gas turbine engines is
supplied
to a heat recovery steam generator (HRSG) that generates steam for driving a
steam
turbine. Power generated by the steam turbine also drives an electrical
generator that
provides electrical power to the power grid.
At least some gasification systems include an injection system that supplies a
gasifier
reactor with process fluids to facilitate at least one exothermic reaction.
Some gasification
systems use multiple types of fuel to drive the gasification process. For
example, a coal
gasification plant primarily utilizes a coal slurry as fuel to drive
gasification which
converts the carbon in the coal into a gaseous fuel to produce electricity.
When the
gasifier is initialized, however, the system components downstream of the
gasification
chamber are not yet at a design point operating pressure, so the process
efficiency is
lacking. Thus, gasification of the coal slurry produces a higher amount of
undesirable
emissions such as sulfur and/or NOX until the downstream components are
brought up to
pressure.
In an attempt to alleviate these emissions issues, cleaner burning fuels, such
as natural
gas are often introduced into the gasification chamber during startup in place
of the coal
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slurry. The natural gas is injected into the gasifier via a dedicated nozzle
separate from
that of the coal slurry.
BRIEF DESCRIPTION OF THE INVENTION
According to one aspect of the invention, an injector tip for a gasifier
combustor nozzle
includes a center body having a plurality of center body openings at a distal
end
configured to inject a fuel flow into a combustion zone of the combustor. One
or more
fuel passages are arranged around the center body and are configured to inject
a fuel
slurry into the combustion zone. One or more oxygen passages are arranged
around the
center body and are configured to inject an oxygen flow into the combustion
zone.
According to another aspect of the invention, a method of fuel injection into
a combustor
includes injecting a first portion of a fuel flow into a combustion zone of
the combustor
through a plurality of center body openings in a distal end of a center body
of an injector
tip. A second portion of the fuel flow is injected into the combustion zone
via one or
more fuel passages arranged around the center body. The injection of the
second portion
of the fuel flow is suspended and a fuel slurry is injected into the
combustion zone via
one or more fuel passages.
These and other advantages and features will become more apparent from the
following
description taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter, which is regarded as the invention, is particularly
pointed out and
distinctly claimed in the claims at the conclusion of the specification. The
foregoing and
other features, and advantages of the invention are apparent from the
following detailed
description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic cross-sectional view of an embodiment of an injector tip
for a
gasifier nozzle;
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FIG. 2 is a schematic of operation of an embodiment of an injector tip for a
gasifier
nozzle during startup operation; and
FIG. 3 is a schematic of operation of an embodiment of an injector tip for a
gasifier
nozzle during coal slurry operation.
The detailed description explains embodiments of the invention, together with
advantages
and features, by way of example with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
Shown in FIG. 1 is an embodiment of an injection nozzle tip 10 for a gasifier.
The nozzle
tip 10 of the embodiment of FIG. 1 includes four separate and distinct
channels for flow
of streams of materials through the nozzle tip 10. First, the nozzle tip 10
includes a
center body 12 which is, in some embodiments, located at a central axis 14 of
the nozzle
tip 10. The center body 12 includes a plurality of center body openings 16
located at a
distal end 18 of the center body 12.
A plurality of fuel passages, or lances, are arranged surrounding the center
body 12. An
inner passage 20 is located around the center body 12, and in some embodiments
is
concentric with the center body 12. A middle passage 22 is located around the
center
body 12 outboard of the inner passage 20, and in some embodiments is
concentric with
the center body 12 and/or the inner passage 20. As shown in FIG. 1, an outer
passage 24
is located around the center body 12 outboard of the middle passage 22, and in
some
embodiments is concentric with the center body 12, the inner passage 20 and/or
the
middle passage 22. In some embodiments, an inner passage end 26, a middle
passage
end 28, and/or an outer passage end 30 are flush with the distal end 18 of the
center body
12.
At startup of the gasifier, as shown in FIG. 2, a fuel flow 32, for example, a
low-sulfur
fuel such as natural gas, is injected into a combustion zone 34 downstream of
the nozzle
tip 10 through the center body 12 via the center body openings 16. The fuel
flow 32 of
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the low sulfur fuel is also injected into the combustion zone 34 through the
middle
passage 22. A flow of primary oxygen 36 is provided to the combustion zone 34
through
the outer passage 24. The primary oxygen 36 is mixed with the fuel flow 32 in
the
combustion zone 34 and combusted therein. In some embodiments, a flow of
secondary
oxygen 38 may be injected into the combustion zone 34 through the inner
passage 20 to
provide further oxygen for combustion with the fuel flow 32.
Referring now to FIG. 3, during coal slurry mode operation of the gasifier,
middle
passage 22 is utilized to convey, a flow of gasifier fuel, such as coal slurry
40 into the
combustion zone 34. Primary oxygen 36 and secondary oxygen 38 are provided
through
the outer passage 24 and the inner passage 20, respectively. Since, during
normal
operation, the flow of coal slurry 40 drives the gasification process, the
fuel flow 32
through the center body 12 is stopped, and a flow of a different fluid 42,
such as carbon
dioxide (which may be recycled), nitrogen, steam, or water, is flowed through
the center
body openings 16. The fluid 42 can be purge gas, moderator gas or cooling
liquid. The
fluid 42 provides cooling to the center body 12, and also prevents plugging of
the center
body openings 16 with particulates from the combustion of the coal slurry 40.
Further,
the fluid 42 prevents burnbacks, combustion products backing upstream through
the
center body openings 16, in the center body 12.
During transitions in operation from, for example, startup operation and coal
slurry mode
operation, both fuel flow 32 and coal slurry 40 may be injected into the
combustion zone
34, with the fuel flow 32 injected through the center body openings 16 and the
coal slurry
40 injected through the middle passage 22. As the transition occurs from
startup (all fuel
flow 32) to coal slurry mode (all coal slurry 40), an amount of each flow can
be gradually
changed to provide a smooth transition between the two modes. For example, as
the
operation moves from startup to coal slurry mode, the amount of fuel flow 32
injected
through the center body openings 16 is gradually decreased while the amount of
coal
slurry 40 injected through the middle passage 22 is gradually increased.
Further,
switching between coal slurry mode and a standby mode, where the flow of coal
slurry 40
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is stopped and injection of the fuel flow 32 is resumed, can occur quickly
since the nozzle
tip 10 has the ability to inject either or both types of fuel via the separate
center body 12
and middle passage 22.
In some embodiments, the inner tip end 26, the middle passage end 28, and/or
the outer
passage end 30 are flush with the distal end 18 of the center body 12. Having
the ends all
flush with each other prevents premixing of the fuels with the primary oxygen,
which
may be detrimental to performance of the gasifier. Further, the flush end
configuration
prevents bumback during coal slurry mode operation.
While the invention has been described in detail in connection with only a
limited
number of embodiments, it should be readily understood that the invention is
not limited
to such disclosed embodiments. Rather, the invention can be modified to
incorporate any
number of variations, alterations, substitutions or equivalent arrangements
not heretofore
described, but which are commensurate with the spirit and scope of the
invention.
Additionally, while various embodiments of the invention have been described,
it is to be
understood that aspects of the invention may include only some of the
described
embodiments. Accordingly, the invention is not to be seen as limited by the
foregoing
description, but is only limited by the scope of the appended claims.
